Creating route in animation

Hello, 

I'm new to AfterEffects and I'm not sure how to do some things, especially this one... So, I have animation like this https://www.youtube.com/watch?v=B54yifaBXW4 ,imagine same thing, but camera goes through nature... and I need to draw a line that follows some route, but don't know how... I have found only examples to do that with pen, but I'm not sure how to do that... Should I draw line for each frame? Something like this: https://www.youtube.com/watch?v=ZABDkbWzcnA (from 0:27)?

Thank you!